Compressor Lubricant Compositions and Preparation Thereof

ABSTRACT

A compressor lubricant composition providing energy savings and exhibiting excellent oxidation stability is provided. The composition comprises (i) 80 to 99.999 weight percent of an isomerized base oil; and (ii) 0.001-20 weight percent of at least an additive selected from an additive package, oxidation inhibitors, pour point depressants, metal deactivators, metal passivators, anti-foaming agents, friction modifiers, anti-wear agents, and mixtures thereof; wherein the isomerized base oil has consecutive numbers of carbon atoms, less than 0.05 wt. % aromatics, a ratio of molecules with monocycloparaffinic functionality to molecules with multicyloparaffinic functionality greater than 2. In one embodiment, compressors employing the lubricant composition with isomerized base oil consumes at least 1% less power than compressors employing the lubricant compositions of the prior art.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit under 35 USC 119 of Provisional Application 61/015114 filed Dec. 19, 2007. This application claims priority to and benefits from the foregoing, the disclosure of which is incorporated herein by reference.

CROSS REFERENCE TO RELATED APPLICATIONS

NONE

TECHNICAL FIELD

The invention relates generally to compressor lubricant compositions, and in one embodiment, compressor lubricant compositions providing energy savings.

BACKGROUND

Approximately 70% of all manufacturers have a compressed air system. These systems power and regulate a variety of equipment, including machine tools, machine handling and separation equipment, spray painting equipment, HVAC systems, etch. They are also used to dry or clean various items in industrial facilities.

Compressed air is one of the most expensive uses of energy in a manufacturing plant. About eight horsepower of electricity is used to generate one horsepower of compressed air. Air compressor energy use may represent 5 to 15% of a typical facility's energy use, depending on process needs. Energy audits by the US Department of Energy (“DOE”) suggest that approximately 8.6% of overall industrial energy consumption can be attributed to air compression. The DOE suggested that over 50% of compressed air systems at small to medium sized industrial facilities have energy efficiency opportunities with low implementation costs (DOE/IAC Industrial Assessment Database, July 1997). Another source has suggested that energy efficient improvements can reduce compressed air system energy use by 20 to 50% (Oregon State University, AIRMaster Compressed Air System Audit and Analysis Software, “How to Take a Self-Guided Tour of Your Compressed Air System,” 1996 revised in 1997, p. 2.).

Suggestions for air compressor improvements include matching compressor with load requirement, using cooler intake air, reducing compressor air pressure, eliminating air leaks, etc. Another energy suggestion relates to compressor lubricants, i.e., “synthetic compressor oils save at least 2% energy in compressors compared to the traditional mineral oils” (http://www.oks-india.com/user/questionanswer.asp) While synthetic lubricants are an improvement over mineral oils in terms of energy saving, they are often not capable of delivering all of the desired performance and physical properties.

In a number of patent publications and applications, i.e., US 2006/0289337, US2006/0201851, US2006/0016721, US2006/0016724, US2006/0076267, US2006/020185, US2006/013210, US2005/0241990, US2005/0077208, US2005/0139513, US2005/0139514, US2005/0133409, US2005/0133407, US2005/0261147, US2005/0261146, US2005/0261145, US2004/0159582, U.S. Pat. No. 7,018,525, U.S. Pat. No. 7,083,713, U.S. application Ser. Nos. 11/400,570, 11/535,165 and 11/613,936, which are incorporated herein by reference, a Fischer Tropsch base oil is produced from a process in which the feed is a waxy feed recovered from a Fischer-Tropsch synthesis. The process comprises a complete or partial hydroisomerization dewaxing step, using a dual-functional catalyst or a catalyst that can isomerize paraffins selectively. Hydroisomerization dewaxing is achieved by contacting the waxy feed with a hydroisomerization catalyst in an isomerization zone under hydroisomerizing conditions. The Fischer-Tropsch synthesis products can be obtained by well-known processes such as, for example, the commercial SASOL® Slurry Phase Fischer-Tropsch technology, the commercial SHELL® Middle Distillate Synthesis (SMDS) Process, or by the non-commercial EXXON® Advanced Gas Conversion (AGC-21) process. Details of these processes and others are described in, for example, EP-A-776959, EP-A-668342; U.S. Pat. Nos. 4,943,672, 5,059,299, 5,733,839, and RE39073 ; and US Published Application No. 2005/0227866, WO-A-9934917, WO-A-9920720 and WO-A-05107935. The Fischer-Tropsch synthesis product usually comprises hydrocarbons having 1 to 100, or even more than 100 carbon atoms, and typically includes paraffins, olefins and oxygenated products. Fischer Tropsch is a viable process to generate clean alternative hydrocarbon products.

There is a still a need for improved compressor lubricants, particularly a compressor lubricant resulting in reduced energy consumption while offering desired performance and physical properties such as long life, oxidation stability, low volatility, and anti-wear properties. There is also a need for an improved compressor lubricant using clean alternative hydrocarbon products such as Fischer Tropsch products.

SUMMARY OF THE INVENTION

In one embodiment, there is provided a compressor lubricant composition comprising (i) 80 to 99.999 weight percent of an isomerized base oil; and (ii) 0.001-20 weight percent of at least an additive selected from an additive package, oxidation inhibitors, pour point depressants, metal deactivators, metal passivators, anti-foaming agents, friction modifiers, anti-wear agents, and mixtures thereof; wherein the isomerized base oil has consecutive numbers of carbon atoms, less than 0.05 wt. % aromatics, a ratio of molecules with monocycloparaffinic functionality to molecules with multicyloparaffinic functionality greater than 2; wherein a compressor employs the composition consumes at least 1% less power than a compressor employing a lubricant composition without the isomerized base oil.

In yet another embodiment, there is provided a compressor lubricant comprising (i) 80 to 99.999 weight percent of an isomerized base oil; and (ii) 0.001-20 weight percent of at least an additive, and wherein the composition shows an evaporation loss of less than 0.75% per IP-48 Oxidation Test (24 hrs.).

In another aspect, there is provided a method save energy while operating compressors, the method comprising using a compressor lubricant composition having excellent oxidation stability, the composition containing: (i) 50 to 99.999 weight percent of an isomerized base oil; and (ii) 0.001-20 weight percent of at least an additive package, wherein the isomerized base oil has consecutive numbers of carbon atoms, less than 0.05 wt. % aromatics, a ratio of molecules with monocycloparaffinic functionality to molecules with multicyloparaffinic functionality greater than 2. The energy saving is at least 1% over the use of compressor lubricants without the isomerized base oil.

DETAILED DESCRIPTION

The following terms will be used throughout the specification and will have the following meanings unless otherwise indicated.

“Fischer-Tropsch derived” means that the product, fraction, or feed originates from or is produced at some stage by a Fischer-Tropsch process. As used herein, “Fischer-Tropsch base oil” may be used interchangeably with “FT base oil,” “FTBO,” “GTL base oil” (GTL: gas-to-liquid), or “Fischer-Tropsch derived base oil.”

As used herein, “isomerized base oil” refers to a base oil made by isomerization of a waxy feed.

As used herein, a “waxy feed” comprises at least 40 wt % n-paraffins. In one embodiment, the waxy feed comprises greater than 50 wt % n-paraffins. In another embodiment, greater than 75 wt % n-paraffins. In one embodiment, the waxy feed also has very low levels of nitrogen and sulphur, e.g., less than 25 ppm total combined nitrogen and sulfur, or in other embodiments less than 20 ppm. Examples of waxy feeds include slack waxes, deoiled slack waxes, refined foots oils, waxy lubricant raffinates, n-paraffin waxes, NAO waxes, waxes produced in chemical plant processes, deoiled petroleum derived waxes, microcrystalline waxes, Fischer-Tropsch waxes, and mixtures thereof. In one embodiment, the waxy feeds have a pour point of greater than 50° C. In another embodiment, greater than 60° C.

“Kinematic viscosity” is a measurement in mm²/s of the resistance to flow of a fluid under gravity, determined by ASTM D445-06.

“Viscosity index” (VI) is an empirical, unit-less number indicating the effect of temperature change on the kinematic viscosity of the oil. The higher the VI of an oil, the lower its tendency to change viscosity with temperature. Viscosity index is measured according to ASTM D 2270-04.

Cold-cranking simulator apparent viscosity (CCS VIS) is a measurement in millipascal seconds, mPa.s to measure the viscometric properties of lubricating base oils under low temperature and low shear. CCS VIS is determined by ASTM D 5293-04.

The boiling range distribution of base oil, by wt %, is determined by simulated distillation (SIMDIS) according to ASTM D 6352-04, “Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 to 700° C. by Gas Chromatography.”

“Noack volatility” is defined as the mass of oil, expressed in weight %, which is lost when the oil is heated at 250° C. with a constant flow of air drawn through it for 60 min., measured according to ASTM D5800-05, Procedure B.

Brookfield viscosity is used to determine the internal fluid-friction of a lubricant during cold temperature operation, which can be measured by ASTM D 2983-04.

“Pour point” is a measurement of the temperature at which a sample of base oil will begin to flow under certain carefully controlled conditions, which can be determined as described in ASTM D 5950-02.

“Auto ignition temperature” is the temperature at which a fluid will ignite spontaneously in contact with air, which can be determined according to ASTM 659-78.

“Ln” refers to natural logarithm with base “e.”

“Traction coefficient” is an indicator of intrinsic lubricant properties, expressed as the dimensionless ratio of the friction force F and the normal force N, where friction is the mechanical force which resists movement or hinders movement between sliding or rolling surfaces. Traction coefficient can be measured with an MTM Traction Measurement System from PCS Instruments, Ltd., configured with a polished 19 mm diameter ball (SAE AISI 52100 steel) angled at 220 to a flat 46 mm diameter polished disk (SAE AISI 52100 steel). The steel ball and disk are independently measured at an average rolling speed of 3 meters per second, a slide to roll ratio of 40 percent, and a load of 20 Newtons. The roll ratio is defined as the difference in sliding speed between the ball and disk divided by the mean speed of the ball and disk, i.e. roll ratio=(Speed1−Speed2)/((Speed1+Speed2)−/2).

As used herein, “consecutive numbers of carbon atoms” means that the base oil has a distribution of hydrocarbon molecules over a range of carbon numbers, with every number of carbon numbers in-between. For example, the base oil may have hydrocarbon molecules ranging from C22 to C36 or from C30 to C60 with every carbon number in-between. The hydrocarbon molecules of the base oil differ from each other by consecutive numbers of carbon atoms, as a consequence of the waxy feed also having consecutive numbers of carbon atoms. For example, in the Fischer-Tropsch hydrocarbon synthesis reaction, the source of carbon atoms is CO and the hydrocarbon molecules are built up one carbon atom at a time. Petroleum-derived waxy feeds have consecutive numbers of carbon atoms. In contrast to an oil based on poly-alpha-olefin (“PAO”), the molecules of an isomerized base oil have a more linear structure, comprising a relatively long backbone with short branches. The classic textbook description of a PAO is a star-shaped molecule, and in particular tridecane, which is illustrated as three decane molecules attached at a central point. While a star-shaped molecule is theoretical, nevertheless PAO molecules have fewer and longer branches that the hydrocarbon molecules that make up the isomerized base oil disclosed herein.

“Molecules with cycloparaffinic functionality” mean any molecule that is, or contains as one or more substituents, a monocyclic or a fused multicyclic saturated hydrocarbon group.

“Molecules with monocycloparaffinic functionality” mean any molecule that is a monocyclic saturated hydrocarbon group of three to seven ring carbons or any molecule that is substituted with a single monocyclic saturated hydrocarbon group of three to seven ring carbons.

“Molecules with multicycloparaffinic functionality” mean any molecule that is a fused multicyclic saturated hydrocarbon ring group of two or more fused rings, any molecule that is substituted with one or more fused multicyclic saturated hydrocarbon ring groups of two or more fused rings, or any molecule that is substituted with more than one monocyclic saturated hydrocarbon group of three to seven ring carbons.

Molecules with cycloparaffinic functionality, molecules with monocycloparaffinic functionality, and molecules with multicycloparaffinic functionality are reported as weight percent and are determined by a combination of Field Ionization Mass Spectroscopy (FIMS), HPLC-UV for aromatics, and Proton NMR for olefins, further fully described herein.

Oxidator BN measures the response of a lubricating oil in a simulated application. High values, or long times to adsorb one liter of oxygen, indicate good stability. Oxidator BN can be measured via a Dornte-type oxygen absorption apparatus (R. W. Dornte “Oxidation of White Oils,” Industrial and Engineering Chemistry, Vol. 28, page 26, 1936), under 1 atmosphere of pure oxygen at 340° F., time to absorb 1000 ml of O₂ by 100 g. of oil is reported. In the Oxidator BN test, 0.8 ml of catalyst is used per 100 grams of oil. The catalyst is a mixture of soluble metal-naphthenates simulating the average metal analysis of used crankcase oil. The additive package is 80 millimoles of zinc bispolypropylenephenyldithiophosphate per 100 grams of oil.

Molecular characterizations can be performed by methods known in the art, including Field Ionization Mass Spectroscopy (FIMS) and n-d-M analysis (ASTM D 3238-95 (Re-approved 2005) with normalization). In FIMS, the base oil is characterized as alkanes and molecules with different numbers of unsaturations. The molecules with different numbers of unsaturations may be comprised of cycloparaffins, olefins, and aromatics. If aromatics are present in significant amount, they would be identified as 4-unsaturations. When olefins are present in significant amounts, they would be identified as 1-unsaturations. The total of the 1-unsaturations, 2-unsaturations, 3-unsaturations, 4-unsaturations, 5-unsaturations, and 6-unsaturations from the FIMS analysis, minus the wt % olefins by proton NMR, and minus the wt % aromatics by HPLC-UV is the total weight percent of molecules with cycloparaffinic functionality. If the aromatics content was not measured, it was assumed to be less than 0.1 wt % and not included in the calculation for total weight percent of molecules with cycloparaffinic functionality. The total weight percent of molecules with cycloparaffinic functionality is the sum of the weight percent of molecules with monocyclopraffinic functionality and the weight percent of molecules with multicycloparaffinic functionality.

Molecular weights are determined by ASTM D2503-92(Reapproved 2002). The method uses thermoelectric measurement of vapour pressure (VPO). In circumstances where there is insufficient sample volume, an alternative method of ASTM D2502-04 may be used; and where this has been used it is indicated.

Density is determined by ASTM D4052-96 (Reapproved 2002). The sample is introduced into an oscillating sample tube and the change in oscillating frequency caused by the change in the mass of the tube is used in conjunction with calibration data to determine the density of the sample.

Weight percent olefins can be determined by proton-NMR according to the steps specified herein. In most tests, the olefins are conventional olefins, i.e. a distributed mixture of those olefin types having hydrogens attached to the double bond carbons such as: alpha, vinylidene, cis, trans, and tri-substituted, with a detectable allylic to olefin integral ratio between 1 and 2.5. When this ratio exceeds 3, it indicates a higher percentage of tri or tetra substituted olefins being present, thus other assumptions known in the analytical art can be made to calculate the number of double bonds in the sample. A solution of 5-10% of the sample in deuterochloroform can be prepared, giving a normal proton spectrum of at least 12 ppm spectral width. Tetramethylsilane (TMS) can be used as an internal reference standard. The instrument used to acquire the spectrum and reference the chemical shift has sufficient gain range to acquire a signal without overloading the receiver/ADC, with a minimum signal digitization dynamic range of at least 65,000 when a 30 degree pulse is applied. The intensities of the proton signals in the region of 0.5-1.9 ppm (methyl, methylene and methine groups), 1.9-2.2 ppm (allylic) and between 6.0-4.5 ppm (olefin) are measured. Using the average molecular weight (estimated by vapor pressure osmometry by ASTM D 2503-92 [re-approved 2002]) of each distillate range paraffin feed, the following can be calculated: (1) the average molecular formula of the saturated hydrocarbons; (2) the average molecular formula of the olefins; (3) the total integral intensity (i.e. the sum of all the integral intensities); (4) the integral intensity per sample hydrogen (i.e. the total integral intensity divided by the number of hydrogens in the formula; (5) the number of olefin hydrogens (i.e. the olefin integral divided by the integral per hydrogen); (6) the number of double bonds (i.e. the olefin hydrogen multiplied by the hydrogens in the olefin formula divided by 2); and (7) the weight percent olefins (i.e. 100 multiplied by the number of double bonds multiplied by the number of hydrogens in a typical olefin molecule divided by the number of hydrogens in a typical distillate range paraffin feed molecule). This Proton NMR procedure to calculate the olefin content of the sample works best when the olefin content is low, e.g., less than about 15 weight percent.

Weight percent aromatics in one embodiment can be measured by HPLC-UV. In one embodiment, the test is conducted using a Hewlett Packard 1050 Series Quaternary Gradient High Performance Liquid Chromatography (HPLC) system, coupled with a HP 1050 Diode-Array UV-Vis detector interfaced to an HP Chem-station. Identification of the individual aromatic classes in the highly saturated base oil can be made on the basis of the UV spectral pattern and the elution time. The amino column used for this analysis differentiates aromatic molecules largely on the basis of their ring-number (or double-bond number). Thus, the single ring aromatic containing molecules elute first, followed by the polycyclic aromatics in order of increasing double bond number per molecule. For aromatics with similar double bond character, those with only alkyl substitution on the ring elute sooner than those with naphthenic substitution. Unequivocal identification of the various base oil aromatic hydrocarbons from their UV absorbance spectra can be accomplished recognizing that their peak electronic transitions are all red-shifted relative to the pure model compound analogs to a degree dependent on the amount of alkyl and naphthenic substitution on the ring system. Quantification of the eluting aromatic compounds can be made by integrating chromatograms made from wavelengths optimized for each general class of compounds over the appropriate retention time window for that aromatic. Retention time window limits for each aromatic class can be determined by manually evaluating the individual absorbance spectra of eluting compounds at different times and assigning them to the appropriate aromatic class based on their qualitative similarity to model compound absorption spectra.

Weight percent aromatic carbon (“Ca”), weight percent naphthenic carbon (“Cn”) and weight percent paraffinic carbon (“Cp”) in one embodiment can be measured by ASTM D3238-95 (Reapproved 2005) with normalization. ASTM D3238-95 (Reapproved 2005) is the Standard Test Method for Calculation of Carbon Distribution and Structural Group Analysis of Petroleum Oils by the n-d-M Method. This method is for “olefin free” feedstocks, i.e., having an olefin content of 2 wt % or less. The normalization process consists of the following: A) If the Ca value is less than zero, Ca is set to zero, and Cn and Cp are increased proportionally so that the sum is 100%. B) If the Cn value is less than zero, Cn is set to zero, and Ca and Cp are increased proportionally so that the sum is 100%; and C) If both Cn and Ca are less than zero, Cn and Ca are set to zero, and Cp is set to 100%.

HPLC-UV Calibration. In one embodiment, HPLC-UV can be used for identifying classes of aromatic compounds even at very low levels, e.g., multi-ring aromatics typically absorb 10 to 200 times more strongly than single-ring aromatics. Alkyl-substitution affects absorption by 20%. Integration limits for the co-eluting 1-ring and 2-ring aromatics at 272 nm can be made by the perpendicular drop method. Wavelength dependent response factors for each general aromatic class can be first determined by constructing Beer's Law plots from pure model compound mixtures based on the nearest spectral peak absorbances to the substituted aromatic analogs. Weight percent concentrations of aromatics can be calculated by assuming that the average molecular weight for each aromatic class was approximately equal to the average molecular weight for the whole base oil sample.

NMR analysis. In one embodiment, the weight percent of all molecules with at least one aromatic function in the purified mono-aromatic standard can be confirmed via long-duration carbon 13 NMR analysis. The NMR results can be translated from % aromatic carbon to % aromatic molecules (to be consistent with HPLC-UV and D 2007) knowing that 95-99% of the aromatics in highly saturated base oils are single-ring aromatics. In another test to accurately measure low levels of all molecules with at least one aromatic function by NMR, the standard D 5292-99 (Reapproved 2004) method can be modified to give a minimum carbon sensitivity of 500:1 (by ASTM standard practice E 386) with a 15-hour duration run on a 400-500 MHz NMR with a 10-12 mm Nalorac probe. Acorn PC integration software can be used to define the shape of the baseline and consistently integrate.

Extent of branching refers to the number of alkyl branches in hydrocarbons. Branching and branching position can be determined using carbon-13 (¹³C) NMR according to the following nine-step process: 1) Identify the CH branch centers and the CH₃ branch termination points using the DEPT Pulse sequence (Doddrell, D. T.; D. T. Pegg; M. R. Bendall, Journal of Magnetic Resonance 1982, 48, 323ff.). 2) Verify the absence of carbons initiating multiple branches (quaternary carbons) using the APT pulse sequence (Patt, S. L.; J. N. Shoolery, Journal of Magnetic Resonance 1982, 46, 535ff.). 3) Assign the various branch carbon resonances to specific branch positions and lengths using tabulated and calculated values known in the art (Lindeman, L. P., Journal of Qualitative Analytical Chemistry 43, 1971 1245ff; Netzel, D. A., et. al., Fuel, 60, 1981, 307ff). 4) Estimate relative branching density at different carbon positions by comparing the integrated intensity of the specific carbon of the methyl/alkyl group to the intensity of a single carbon (which is equal to total integral/number of carbons per molecule in the mixture). For the 2-methyl branch, where both the terminal and the branch methyl occur at the same resonance position, the intensity is divided by two before estimating the branching density. If the 4-methyl branch fraction is calculated and tabulated, its contribution to the 4+methyls is subtracted to avoid double counting. 5) Calculate the average carbon number. The average carbon number is determined by dividing the molecular weight of the sample by 14 (the formula weight of CH₂). 6) The number of branches per molecule is the sum of the branches found in step 4. 7) The number of alkyl branches per 100 carbon atoms is calculated from the number of branches per molecule (step 6) times 100 /average carbon number. 8) Estimate Branching Index (BI) by ¹H NMR Analysis, which is presented as percentage of methyl hydrogen (chemical shift range 0.6-1.05 ppm) among total hydrogen as estimated by NMR in the liquid hydrocarbon composition. 9) Estimate Branching proximity (BP) by 13C NMR, which is presented as percentage of recurring methylene carbons—which are four or more carbons away from the end group or a branch (represented by a NMR signal at 29.9 ppm) among total carbons as estimated by NMR in the liquid hydrocarbon composition. The measurements can be performed using any Fourier Transform NMR spectrometer, e.g., one having a magnet of 7.0 T or greater. After verification by Mass Spectrometry, UV or an NMR survey that aromatic carbons are absent, the spectral width for the ¹³C NMR studies can be limited to the saturated carbon region, 0-80 ppm vs. TMS (tetramethylsilane). Solutions of 25-50 wt. % in chloroform-d1 are excited by 30 degrees pulses followed by a 1.3 seconds (sec.) acquisition time. In order to minimize non-uniform intensity data, the broadband proton inverse-gated decoupling is used during a 6 sec. delay prior to the excitation pulse and on during acquisition. Samples are doped with 0.03 to 0.05 M Cr (acac)₃ (tris(acetylacetonato)-chromium (III)) as a relaxation agent to ensure full intensities are observed. The DEPT and APT sequences can be carried out according to literature descriptions with minor deviations described in the Varian or Bruker operating manuals. DEPT is Distortionless Enhancement by Polarization Transfer. The DEPT 45 sequence gives a signal all carbons bonded to protons. DEPT 90 shows CH carbons only. DEPT 135 shows CH and CH₃ up and CH₂ 180 degrees out of phase (down). APT is attached proton test, known in the art. It allows all carbons to be seen, but if CH and CH₃ are up, then quaternaries and CH₂ are down. The branching properties of the sample can be determined by ¹³C NMR using the assumption in the calculations that the entire sample was iso-paraffinic. The unsaturates content may be measured using Field Ionization Mass Spectroscopy (FIMS).

The one embodiment, the compressor lubricant composition comprises 0.001 to 20 wt % of at least an additive in a matrix of base oil or base oil blends.

Base Oil Component: In one embodiment, the base oil or blend thereof comprises at least an isomerized base oil which the product itself, its fraction, or feed originates from or is produced at some stage by isomerization of a waxy feed from a Fischer-Tropsch process (“Fischer-Tropsch derived base oils”). In another embodiment, the base oil comprises at least an isomerized base oil made from a substantially paraffinic wax feed (“waxy feed”). In a third embodiment, the isomerized base oil comprises mixtures of products made from a substantially paraffinic wax feed as well as products made from a waxy feed from a Fischer-Tropsch process.

Fischer-Tropsch derived base oils are disclosed in a number of patent publications, including for example U.S. Pat. Nos. 6,080,301, 6,090,989, and 6,165,949, and US Patent Publication No. US2004/0079678A1, US20050133409, US20060289337. The Fischer-Tropsch process is a catalyzed chemical reaction in which carbon monoxide and hydrogen are converted into liquid hydrocarbons of various forms including a light reaction product and a waxy reaction product, with both being substantially paraffinic.

In one embodiment the isomerized base oil has consecutive numbers of carbon atoms and has less than 25 wt % naphthenic carbon by n-d-M with normalization. In another embodiment, the amount of naphthenic carbon is less than 10 wt. %. In yet another embodiment the isomerized base oil made from a waxy feed has a kinematic viscosity at 100+ C. between 1.5 and 3.5 mm²/s.

In one embodiment, the isomerized base oil is made by a process in which the hydroisomerization dewaxing is performed at conditions sufficient for the base oil to have: a) a weight percent of all molecules with at least one aromatic functionality less than 0.30; b) a weight percent of all molecules with at least one cycloparaffinic functionality greater than 10; c) a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 20 and d) a viscosity index greater than 28×Ln (Kinematic viscosity at 100° C.)+80.

In another embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized using a shape selective intermediate pore size molecular sieve comprising a noble metal hydrogenation component, and under conditions of 600-750° F. (315-399° C.) In the process, the conditions for hydroisomerization are controlled such that the conversion of the compounds boiling above 700° F. (371° C.) in the wax feed to compounds boiling below 700° F. (371° C.) is maintained between 10 wt % and 50 wt %. A resulting isomerized base oil has a kinematic viscosity of between 1.0 and 3.5 mm²/s at 100° C. and a Noack volatility of less than 50 weight %. The base oil comprises greater than 3 weight % molecules with cycloparaffinic functionality and less than 0.30 weight percent aromatics.

In one embodiment the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 1000×(Kinematic Viscosity at 100° C.)^(−2.7). In another embodiment, the isomerized base oil has a Noack volatility less than an amount calculated by the following equation: 900×(Kinematic Viscosity at 100° C.)⁻2.8. In a third embodiment, the isomerized base oil has a Kinematic Viscosity at 100° C. of >1.808 mm²/s and a Noack volatility less than an amount calculated by the following equation: 1.286+20 (kv100)^(−1.5)+551.8 e^(−kv100), where kv100 is the kinematic viscosity at 100° C. In a fourth embodiment, the isomerized base oil has a kinematic viscosity at 100° C. of less than 4.0 mm²/s, and a wt % Noack volatility between 0 and 100. In a fifth embodiment, the isomerized base oil has a kinematic viscosity between 1.5 and 4.0 mm²/s and a Noack volatility less than the Noack volatility calculated by the following equation: 160-40 (Kinematic Viscosity at 100° C.).

In one embodiment, the isomerized base oil has a kinematic viscosity at 100° C. in the range of 2.4 and 3.8 mm²/s and a Noack volatility less than an amount defined by the equation: 900×(Kinematic Viscosity at 100° C.)^(−2.8)−15). For kinematic viscosities in the range of 2.4 and 3.8 mm²/s, the equation: 900×(Kinematic Viscosity at 100° C.)^(−2.8)−15) provides a lower Noack volatility than the equation: 160-40 (Kinematic Viscosity at 100° C.)

In one embodiment, the isomerized base oil is made from a process in which the highly paraffinic wax is hydroisomerized under conditions for the base oil to have a kinematic viscosity at 100° C. of 3.6 to 4.2 mm²/s, a viscosity index of greater than 130, a wt % Noack volatility less than 12, a pour point of less than −9° C.

In one embodiment, the isomerized base oil has an aniline point, in degrees F., greater than 200 and less than or equal to an amount defined by the equation: 36×Ln(Kinematic Viscosity at 100° C., in mm²/s)+200.

In one embodiment, the isomerized base oil has an auto-ignition temperature (AIT) greater than the AIT defined by the equation: AIT in ° C.=1.6×(Kinematic Viscosity at 40° C., in mm2/s)+300. In a second embodiment, the base oil as an AIT of greater than 329° C. and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C., in mm²/s)+100.

In one embodiment, the isomerized base oil has a relatively low traction coefficient, specifically, its traction coefficient is less than an amount calculated by the equation: traction coefficient=0.009×Ln (kinematic viscosity in mm²/s)−0.001, wherein the kinematic viscosity in the equation is the kinematic viscosity during the traction coefficient measurement and is between 2 and 50 mm²/s. In one embodiment, the isomerized base oil has a traction coefficient of less than 0.023 (or less than 0.021) when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a traction coefficient of less than 0.017 when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40%. In another embodiment the isomerized base oil has a viscosity index greater than 150 and a traction coefficient less than 0.015 when measured at a kinematic viscosity of 15 mm²/s and at a slide to roll ratio of 40 percent.

In some embodiments, the isomerized base oil having low traction coefficients also displays a higher kinematic viscosity and higher boiling points. In one embodiment, the base oil has a traction coefficient less than 0.015, and a 50 wt % boiling point greater than 565° C. (1050° F.). In another embodiment, the base oil has a traction coefficient less than 0.011 and a 50 wt % boiling point by ASTM D 6352-04 greater than 582° C. (1080° F.).

In some embodiments, the isomerized base oil having low traction coefficients also displays unique branching properties by NMR, including a branching index less than or equal to 23.4, a branching proximity greater than or equal to 22.0, and a Free Carbon Index between 9 and 30. In one embodiment, the base oil has at least 4 wt % naphthenic carbon, in another embodiment, at least 5 wt % naphthenic carbon by n-d-M analysis by ASTM D 3238-95 (Reapproved 2005) with normalization.

In one embodiment, the isomerized base oil is produced in a process wherein the intermediate oil isomerate comprises paraffinic hydrocarbon components, and in which the extent of branching is less than 7 alkyl branches per 100 carbons, and wherein the base oil comprises paraffinic hydrocarbon components in which the extent of branching is less than 8 alkyl branches per 100 carbons and less than 20 wt % of the alkyl branches are at the 2 position. In one embodiment, the FT base oil has a pour point of less than −8° C.; a kinematic viscosity at 100° C. of at least 3.2 mm²/s; and a viscosity index greater than a viscosity index calculated by the equation of=22×Ln (kinematic viscosity at 100° C.)+132.

In one embodiment, the base oil comprises greater than 10 wt. % and less than 70 wt. % total molecules with cycloparaffinic functionality, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality greater than 15.

In one embodiment, the isomerized base oil has an average molecular weight between 600 and 1100, and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms. In another embodiment, the isomerized base oil has a kinematic viscosity between about 8 and about 25 mm²/s and an average degree of branching in the molecules between 6.5 and 10 alkyl branches per 100 carbon atoms.

In one embodiment, the isomerized base oil is obtained from a process in which the highly paraffinic wax is hydroisomerized at a hydrogen to feed ratio from 712.4 to 3562 liter H₂/liter oil, for the base oil to have a total weight percent of molecules with cycloparaffinic functionality of greater than 10, and a ratio of weight percent molecules with monocycloparaffinic functionality to weight percent molecules with multicycloparaffinic functionality of greater than 15. In another embodiment, the base oil has a viscosity index greater than an amount defined by the equation: 28×Ln (Kinematic viscosity at 100° C.)+95. In a third embodiment, the base oil comprises a weight percent aromatics less than 0.30; a weight percent of molecules with cycloparaffinic functionality greater than 10; a ratio of weight percent of molecules with monocycloparaffinic functionality to weight percent of molecules with multicycloparaffinic functionality greater than 20; and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+110. In a fourth embodiment, the base oil further has a kinematic viscosity at 100° C. greater than 6 mm²/s. In a fifth embodiment, the base oil has a weight percent aromatics less than 0.05 and a viscosity index greater than 28×Ln (Kinematic Viscosity at 100° C.)+95. In a sixth embodiment, the base oil has a weight percent aromatics less than 0.30, a weight percent molecules with cycloparaffinic functionality greater than the kinematic viscosity at 100° C., in mm²/s, multiplied by three, and a ratio of molecules with monocycloparaffinic functionality to molecules with multicycloparaffinic functionality greater than 15.

In one embodiment, the isomerized base oil contains between 2 and 10 wt % naphthenic carbon as measured by n-d-M. In one embodiment, the base oil has a kinematic viscosity of 1.5-3.0 mm²/s at 100° C. and 2-3 wt % naphthenic carbon. In another embodiment, a kinematic viscosity of 1.8-3.5 mm²/s at 100° C. and 2.5-4 wt % naphthenic carbon. In a third embodiment, a kinematic viscosity of 3-6 mm²/s at 100° C. and 2.7-5 wt % naphthenic carbon. In a fourth embodiment, a kinematic viscosity of 10-30 mm²/s at 100° C. and between greater than 5.2% and less than 25 wt % naphthenic carbon.

In one embodiment, the isomerized base oil has an average molecular weight greater than 475; a viscosity index greater than 140, and a weight percent olefins less than 10. The base oil improves the air release and low foaming characteristics of the mixture when incorporated into the compressor lubricant composition.

In one embodiment of a compressor oil composition for use in an application requiring a food grade lubricant for incidental contact with food for human consumption application, the isomerized base oil is a white oil as disclosed in U.S. Pat. No. 7,214,307 and US Patent Publication US20060016724. In one embodiment, the isomerized base oil is a white oil having a kinematic viscosity at 100° C. between about 1.5 cSt and 36 mm²/s, a viscosity index greater than an amount calculated by the equation: Viscosity Index=28×Ln (the Kinematic Viscosity at 100° C.)+95, between 5 and less than 18 weight percent molecules with cycloparaffinic functionality, less than 1.2 weight percent molecules with multicycloparaffinic functionality, a pour point less than 0° C. and a Saybolt color of +20 or greater.

In one embodiment, the compressor lubricant composition employs a base oil that consists of at least one of the isomerized base oils described above. In another embodiment, the composition consists essentially of at least a Fischer-Tropsch base oil. In yet another embodiment, the composition employs at least an isomerized base oil, e.g., a Fischer-Tropsch base oil, and optionally 5 to 20 wt. % of at least another type of oil, e.g., lubricant base oils selected from Group I, II, III, IV, and V lubricant base oils as defined in the API Interchange Guidelines, and mixtures thereof. Examples include conventionally used mineral oils, synthetic hydrocarbon oils or synthetic ester oils, or mixtures thereof depending on the application. Mineral lubricating oil base stocks can be any conventionally refined base stocks derived from paraffinic, naphthenic and mixed base crudes. Synthetic lubricating oils that can be used include esters of glycols and complex esters. Other synthetic oils that can be used include synthetic hydrocarbons such as polyalphaolefins; alkyl benzenes, e.g., alkylate bottoms from the alkylation of benzene with tetrapropylene, or the copolymers of ethylene and propylene; silicone oils, e.g., ethyl phenyl polysiloxanes, methyl polysiloxanes, etc., polyglycol oils, e.g., those obtained by condensing butyl alcohol with propylene oxide; etc. Other suitable synthetic oils include the polyphenyl ethers, e.g., those having from 3 to 7 ether linkages and 4 to 8 phenyl groups. Other suitable synthetic oils include polyisobutenes, and alkylated aromatics such as alkylated naphthalenes.

In one embodiment, the compressor lubricant composition employs a base oil consisting essentially of at least a FT base oil having a kinematic viscosity at 100° C. between 6 and 16 mm²/s; a kinematic viscosity at 40° C. between 25 mm2/s and 120 mm²/s; a viscosity index between 140 and 170; CCS VIS in the range of 1,500-15,000 mPa.s at −25° C.; pour point in the range of −10 and −30° C.; molecular weight of 500-750; density in the range of 0.800 to 0.840; paraffinic carbon in the range of 93-97%; naphthenic carbon in the range of 3-8%; Oxidator BN of 15 to 50 hours; and Noack volatility in wt. % of 0.5 to 5 as measured by ASTM D5800-05 Procedure B; and less than 0.05 wt. % aromatics and a molecular weight of 500 to 800 by ASTM D 2503-92 (Reapproved 2002).

In another embodiment, the compressor lubricant composition employs a base oil consisting essentially of a mixture of isomerized base oils to give the desired performance properties needed for the application.

Additional Components: The compressor oil composition in one embodiment further comprises additives including but not limited to extreme pressure additives, anti-wear additives, metal passivators/deactivators, metallic detergents, corrosion inhibitors, foam inhibitors and/or demulsifiers, anti-oxidants, friction modifiers, pour point depressants, viscosity index modifiers, in an amount of 0.01 to 20 wt. %.

In one embodiment, the compressor lubricant composition further comprises antioxidants (oxidation additives) in an amount of 0.01 to 5 wt. %. Examples of useful antioxidants include are phenyl naphthylamines, i.e., both alpha and beta-naphthyl amines; diphenyl amine; iminodibenzyl; p,p′-dioctyl-diphenylamine; and related aromatic amines. In another embodiment, useful antioxidants include the group of phenolic antioxidants, aromatic amine antioxidants, sulfurized phenolic antioxidants, and organic phosphites, among others. Examples of phenolic antioxidants include 2,6-di-tert-butylphenol, liquid mixtures of tertiary butylated phenols, 2,6-di-tert-butyl-4-methylphenol, 4,4′-methylenebis(2,6-di-tert-butylphenol), 2,2′-methylenebis(4-methyl6-tert-butylphenol), mixed methylene-bridged polyalkyl phenols, 4,4′-thiobis(2-methyl-6-tert-butylphenol), 4,4′-butylidene-bis(3-methyl-6-tert-butylphenol), 4,4′-isopropylidene-bis(2,6-di-tert-butylphenol), 2,2′-methylene-bis(4-methyl-6-nonylphenol), 2,2′-isobutylidene-bis(4,6-dimethylphenol), 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,4-dimethyl-6-tert-butyl-phenol, 2,6-di-tert-1-dimethylamino-p-cresol, 2,6-di-tert-4-(N,N′-dimethylaminomethylphenol), 4,4′-thiobis(2-methyl-6-tert-butylphenol), 2,2′-thiobis(4-methyl-6-tert-butylphenol), bis(3-methyl-4-hydroxy-5-tert-10-butylbenzyl)-sulfide, bis(3,5-di-tert-butyl-4-hydroxybenzyl), 2,2′-5-methylene-bis(4-methyl-6-cyclohexylphenol), N,N′-di-sec-butylphenylenediamine, 4-isopropylaminodiphenylamine, phenyl-.alpha.-naphthyl amine, phenyl-.alpha.-naphthyl amine, and ring-alkylated diphenylamines. Examples include the sterically hindered tertiary butylated phenols, bisphenols and cinnamic acid derivatives and combinations thereof. In yet another embodiment, the antioxidant is an organic phosphonate having at least one direct carbon-to-phosphorus linkage. Diphenylamine-type oxidation inhibitors include, but are not limited to, alkylated diphenylamine, phenyl-alpha-naphthylamine, and alkylated-alpha-naphthylamine. Other types of oxidation inhibitors include metal dithiocarbamate (e.g., zinc dithiocarbamate), and 15-methylenebis(dibutyldithiocarbamate).

In one embodiment, the compressor lubricant composition optionally comprises 0.01 to 1 wt. % of a foam inhibitor. Examples of foam inhibitors include but are not limited to polysiloxanes, dimethyl polycyclohexane and polyacrylates.

In one embodiment, the compressor lubricant composition further comprises 0.001 to 0.5 wt. % of at least a metal deactivators. Examples of suitable cuprous metal deactivators include imidazole, benzimidazole, pyrazole, benzotriazole, tolutriazole, 2-methyl benzimidazole, 3,5-dimethyl pyrazole, and methylene bis-benzotriazole.

In one embodiment, the compressor lubricant composition comprises 0.001 to 6 wt. %. of at least a viscosity index modifier. In one embodiment, the viscosity index modifiers used is a mixture of modifiers selected from polyacrylate or polymethacrylate and polymers, comprising vinyl aromatic units and esterified carboxyl-containing units. In one embodiment, the first viscosity modifier is a polyacrylate or polymethacrylate having an average molecular weight of 10,000 to 60,000. In another embodiment, the second viscosity modifier comprises vinyl aromatic units and esterified carboxyl-containing units, having an average molecular weight of 100,000 to 200,000. In another embodiment, the viscosity modifier is a blend of a polymethacrylate viscosity index improver having a weight average molecular weight of 25,000 to 150,000 and a shear stability index less than 5 and a polymethacrylate viscosity index improver having a weight average molecular weight of 500,000 to 1,000,000 and a shear stability index of 25 to 60. In yet another embodiment, the viscosity modifier is selected from the group of polymethacrylate type polymers, ethylene-propylene copolymers, styrene-isoprene copolymers, hydrated styrene-isoprene copolymers, polyisobutylene, and mixtures thereof.

In one embodiment, the compressor lubricant further comprises at least a surfactant, or also known as a dispersant, which can be generally classified as anionic, cationic, zwitterionic, or non-ionic. In some embodiments a dispersant may be used alone or in combination of one or more species or types of dispersants. Examples include an oil-soluble dispersant selected from the group consisting of succinimide dispersants, succinic ester dispersants, succinic ester-amide dispersant, Mannich base dispersant, phosphorylated forms thereof, and boronated forms thereof. The dispersants may be capped with acidic molecules capable of reacting with secondary amino groups. The molecular weight of the hydrocarbyl groups may range from 600 to 3000, for example from 750 to 2500, and as a further example from 900 to 1500. In one embodiment, the dispersant is selected from the group of alkenyl succinimides, alkenyl succinimides modified with other organic compounds, alkenyl succinimides modified by post-treatment with ethylene carbonate or boric acid, pentaerythritols, phenate-salicylates and their post-treated analogs, alkali metal or mixed alkali metal, alkaline earth metal borates, dispersions of hydrated alkali metal borates, dispersions of alkaline-earth metal borates, polyamide ashless dispersants and the like or mixtures of such dispersants.

In one embodiment, the compressor lubricant further comprises one or more metallic detergents. Examples of metallic detergent include an oil-soluble neutral or overbased salt of alkali or alkaline earth metal with one or more of the following acidic substances (or mixtures thereof): (1) a sulfonic acid, (2) a carboxylic acid, (3) a salicylic acid, (4) an alkyl phenol, (5) a sulfurized alkyl phenol, and (6) an organic phosphorus acid characterized by at least one direct carbon-to-phosphorus linkage, such as phosphonate.

In one embodiment, the compressor lubricant further comprises at least a corrosion inhibitor. Examples of suitable ferrous metal corrosion inhibitors are the metal sulfonates such as calcium petroleum sulfonate, barium dinonylnaphthalene sulfonate and basic barium dinonylnaphthalene sulfonate, carbonated or non-carbonated. Other examples are selected from thiazoles, triazoles, and thiadiazoles. Examples of such compounds include benzotriazole, tolyltriazole, octyltriazole, decyltriazole, dodecyltriazole, 2-mercapto benzothiazole, 2,5-dimercapto-1,3,4-thiadiazole, 2-mercapto-5-hydrocarbylthio-1,3,4-thiadiazoles, 2-mercapto-5-hydrocarbyldithio-1,3,4-thiadiazoles, 2,5-bis(hydrocarbylthio)-1,3,4-thiadiazoles, and 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazoles. Suitable compounds include the 1,3,4-thiadiazoles, a number of which are available as articles of commerce, and also combinations of triazoles such as tolyltriazole with a 1,3,5-thiadiazole such as 2,5-bis(alkyldithio)-1,3,4-thiadiazole. The 1,3,4-thiadiazoles are generally synthesized from hydrazine and carbon disulfide by known procedures. See, for example, U.S. Pat. Nos. 2,765,289; 2,749,311; 2,760,933; 2,850,453; 2,910,439; 3,663,561; 3,862,798; and 3,840,549.

In one embodiment, the rust or corrosion inhibitors are selected from the group of monocarboxylic acids and polycarboxylic acids. Examples include octanoic acid, decanoic acid and dodecanoic acid. Suitable polycarboxylic acids include dimer and trimer acids produced from acids such as tall oil fatty acids, oleic acid, linoleic acid, or the like. Another useful type of rust inhibitor may comprise alkenyl succinic acid and alkenyl succinic anhydride corrosion inhibitors, for example, tetrapropenylsuccinic acid, tetrapropenylsuccinic anhydride, tetradecenylsuccinic acid, tetradecenylsuccinic anhydride, hexadecenylsuccinic acid, hexadecenylsuccinic anhydride, and the like. Also useful are the half esters of alkenyl succinic acids having 8 to 24 carbon atoms in the alkenyl group with alcohols such as the polyglycols. Other suitable rust or corrosion inhibitors include ether amines; acid phosphates; amines; polyethoxylated compounds such as ethoxylated amines, ethoxylated phenols, and ethoxylated alcohols; imidazolines; aminosuccinic acids or derivatives thereof, and the like. Mixtures of such rust or corrosion inhibitors can be used. Other examples of rust inhibitors include a polyethoxylated phenol, neutral calcium sulfonate and basic calcium sulfonate.

In one embodiment, the compressor lubricant further comprise at least a friction modifier selected from the group of succinimide, a bis-succinimide, an alkylated fatty amine, an ethoxylated fatty amine, an amide, a glycerol ester, an imidazoline, fatty alcohol, fatty acid, amine, borated ester, other esters, phosphates, phosphites, phosphonates, and mixtures thereof.

In one embodiment, the compressor lubricant optionally comprises a sufficient amount of pour point depressant to cause the pour point of the compressor lubricant to be at least 3° C. below the pour point of a blend that does not have the pour point depressant. Pour point depressants are known in the art and include, but are not limited to esters of maleic anhydride-styrene copolymers, polymethacrylates, polyacrylates, polyacrylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids, ethylene-vinyl acetate copolymers, alkyl phenol formaldehyde condensation resins, alkyl vinyl ethers, olefin copolymers, and mixtures thereof.

In one embodiment, the compressor lubricant further comprises at least an extreme pressure anti-wear agent (EP/AW Agent) in the range of from 0.1 to 3.0 wt. %, based on the total weight of lubricating oil composition. Examples of such agents include, but are not limited to, phosphates, carbarmates, esters, molybdenum-containing compounds, boron-containing compounds and ashless anti-wear additives such as substituted or unsubstituted thiophosphoric acids, and salts thereof.

In one embodiment, the anti-wear agents are selected from the group of zinc dialky-1-dithiophosphate (primary alkyl, secondary alkyl, and aryl type), diphenyl sulfide, methyl trichlorostearate, chlorinated naphthalene, fluoroalkylpolysiloxane, lead naphthenate, neutralized phosphates, dithiophosphates, and sulfur-free phosphates. In another embodiment, the anti-wear agent is selected from the group of a zinc dialkyl dithio phosphate (ZDDP), an alkyl phosphite, a trialkyl phosphite, and amine salts of dialkyl and mono-alkyl phosphoric acid. Examples of such molybdenum-containing compounds include molybdenum dithiocarbamates, trinuclear molybdenum compounds, for example as described in WO-A-98/26030, sulphides of molybdenum and molybdenum dithiophosphate. Boron-containing compounds include borate esters, borated fatty amines, borated epoxides, alkali metal (or mixed alkali metal or alkaline earth metal) borates and borated overbased metal salts.

The compressor lubricant may also include conventional additives in addition to those described above. Examples include but are not limited to colorants, metal deactivators such as disalicylidene propylenediamine, triazole derivatives, thiadiazole derivatives, and mercaptobenzimidazoles, antifoam and defoamer additives such as alkyl methacrylate polymers and dimethyl silicone polymers, and/or air expulsion additives. Such additives may be added to provide, for example, viscometric multigrade functionality.

In one embodiment, the additional components are added as a fully formulated additive package fully formulated to meet an original equipment manufacturer's requirements. The package to be used depends in part by the requirements of the specific equipment to receive the lubricant composition. Some of the above-mentioned additives can provide a multiplicity of effects; thus for example, a single additive may act as a dispersant as well as an oxidation inhibitor. In one embodiment, when the compressor lubricant contains one or more of the above-mentioned additives, each additive is typically blended into the base oil in an amount that enables the additive to provide its desired function. It may be desirable, although not essential, to prepare one or more additive concentrates comprising additives (concentrates containing at least one of above-mentioned additives sometimes being referred to as “additive packages”) to add to the compressor lubricant composition. The final composition may employ from about 0.001 to 20 wt. % of the concentrate, the remainder being the oil of lubricating viscosity. The components can be blended in any order and can be blended as combinations of components.

Method for Making: Additives used in formulating the compressor lubricant composition can be blended into the base oil matrix individually or in various sub-combinations to subsequently form the compressor lubricant. In one embodiment, all of the components are blended concurrently using an additive concentrate (i.e., additives plus a diluent, such as a hydrocarbon solvent). The use of an additive concentrate takes advantage of the mutual compatibility afforded by the combination of ingredients when in the form of an additive concentrate.

In another embodiment, the compressor lubricant composition is prepared by mixing the base oil matrix with the separate additives or additive package(s) at an appropriate temperature, such as approximately 60° C., until homogeneous.

Applications: The composition can be used in various compressor applications including reciprocating compressors as well as screw compressors. In one embodiment with a white oil as the isomerized base oil, the compressor lubricant composition is suitable for use in hypercompressors requiring food grade lubricants for incidental contact with food for human consumption.

Properties: In one embodiment, the composition when used as a lubricant for compressors, e.g., reciprocating compressors as well as screw compressors, allows the compressors to consume less energy while still provides the same performance specifications. In one embodiment, the composition provides energy (power or electricity) savings of at least as compared to the traditional compressor lubricants comprising synthetic oils. In another embodiment, the composition provides an energy saving of at least 5%, as compared to traditional compressor lubricants comprising mineral oils and/or synthetic oils. In a third embodiment, the composition provides an energy saving of at least 5%, as compared to the traditional compressor lubricants of the prior art.

In one embodiment, the compressor lubricant composition is characterized as meeting or exceeding the German standard DIN 51 506 class VDL specifications and exhibiting high load carrying capacity. In another embodiment, the composition meets or exceeds ISO/DP 6521-L-DAB for medium duty applications. In a third embodiment, the composition meets or exceeds ISO 6743-3A-DAC for heavy duty applications.

In one embodiment, the compressor lubricant composition is suitable for use in oil injected rotary screw compressors operating at high discharge temperatures (>100° C.) and high discharge pressures (>15 bar). In another embodiment, the composition meets the requirements for reciprocating air compressors operating at high discharge temperatures (>200° C.). In yet another embodiment, the compressor oil composition is suitable for use in stationary and portable compressors, operating at compression temperatures up to 220° C. including compressors with oil lubricated pressure space, e.g. single and multistage reciprocating compressors or single or multistage centrifugal compressors.

In one embodiment, the composition is characterized as having excellent demulsibility characteristics, thus allowing excess water to be drained off. Demulsification of compressor oil can cause sludge, plug filters, shorten oil life, cause foaming and reduce lubricant performance. Complete demulsibility minimizes environmental discharges. In one embodiment, the compressor lubricant composition separates from water in less than 60 minutes as measured according to ASTM D-1401-2002. In another embodiment, the composition separates from water in less than 45 minutes as measured according to ASTM D-1401-2002. In a third embodiment, the composition separates from water in less than 30 minutes as measured according to ASTM D-1401-2002.

In one embodiment, the compressor lubricant composition is characterized as having a high viscosity index, e.g., greater than 140, demonstrating excellent viscosity stability over a wide temperature range with better protection at high temperatures as well as better oil flow at lower temperatures. In one embodiment, the compressor lubricant composition is characterized as being very stable for use with a wide range of temperatures with a viscosity index (VI) of at least 150. In another embodiment, the compressor lubricant has a VI of at least 155. In a third embodiment, a VI of at least 160.

Depending on the isomerized base oils for use as the base oil, the compressor lubricant composition in one embodiment is tailored to meet any of the ISO viscosity grades, including ISO 68, ISO 100, or ISO 150. In one another embodiment, the compressor lubricant composition is tailored to have a viscosity of ISO 46 (41.4 to 50.6 mm2/s at 40° C. range).

In one embodiment, the compressor lubricant composition is characterized as being particularly suitable for use in applications demanding the use of fire resistant fluids, e.g., a power plant application, with a flash point of at least 250° C. In a second embodiment, the compressor lubricant has a flash point of at least 270° C. In one embodiment, the compressor lubricant composition has an auto-ignition temperature of at least 360° C.

In one embodiment, the compressor lubricant composition demonstrates excellent oxidation stability as measured according to ASTM D2272-02 with a RPVOT of greater than 300 minutes. In another embodiment, the RPVOT is greater than 600 minutes. In yet another embodiment, the RPVOT is greater than 1000 minutes. In a fourth embodiment, the RPVOT is greater than 1200 minutes.

In one embodiment, the composition demonstrates excellent oxidation stability according to IP-48 Oxidation Test (24 hrs.) with an evaporation loss measured of less than 1%. In a second embodiment, the evaporation loss is less than 0.75%. In a third embodiment, the evaporation loss is equal or less than 0.5%.

In one embodiment, the composition demonstrate excellent thermal oxidative stability as demonstrated in the Panel Coker test, with minimal or zero deposit at high temperatures (e.g., 560° F., 580° F., and 600° F.) compared to the compositions of the prior art. In the Panel Coker test, the cleaner the panel, the better the oil as a clean panel indicates less residual carbon/residue from thermal degradation.

In one embodiment, the compressor lubricant composition exhibits reduced mist formation property and imparts aerosol control or particulate control to the fluid, e.g., having 5 to 50% mist reduction compared to compressor lubricant compositions comprising mineral oils in the prior art.

The following Examples are given as non-limitative illustration of aspects of the present invention.

EXAMPLES

The Examples were prepared by mixing the components in the amounts (in weight percent) as indicated in the tables. The components used in the examples are listed as follows:

FTBO-H, FTBO-M, FTBO-249, FTBO417, FTBO-780, and FTBO-782 are isomerized base oils from Chevron Corporation of San Ramon, Calif. The properties of the FTBO base oils used in the examples are shown in Table 5.

Chevron™ 220R and Chevron™ 600R are conventional Group II base oils from Chevron Corporation of San Ramon, Calif.

PAO-1, PAO-2 and PAO-3 are commercially available polyalpha olefin (“PAO”) base oils.

SN-1 and SN-2 are solvent neutral base oils (Group I), commercially available from a number of sources.

Group III is a commercially available high viscosity index mineral base oil having a viscosity of about 6.8 mm²/s cSt at 100° C. and a viscosity index of 144.

Group IV is a commercially available high viscosity grade API Group IV base oil.

Synthetic Oil 1 is a synthetic ester.

Synthetic Oil 2 is another synthetic ester.

Group II is commercially available API Group II base oil.

Additive 1 is a synthetic ester.

Additive 2 is an anti-wear additive, also commercially available.

Additive 3 is an amine anti-oxidant.

Additive 4 is a general purpose, ashless antioxidant.

Additive 5 is an anti-wear agent.

Additive 6 is a metal deactivator.

Additive 7 is an anti foamant.

Additive 8 is a corrosion inhibitor.

Additive 9 is a commercially available hydraulic oil additive package.

Additive 10 is a pour point depressant.

Additive 11 is a commercially available anti-foaming agent.

Additive 12 is a commercially available amine antioxidant.

Additive 13 is a commercially available amine antioxidant.

Additive 14 is a commercially available phenolic antioxidant.

Additive 15 is a commercially available metal deactivator.

Additive 16 is a corrosion inhibitor.

Additive 17 is another commercially available corrosion inhibitor.

Additive 18 is commercially ester anti-wear additive.

Additive 19 is a commercially available pour point depressant.

Additive 20 is a commercially available defoaming agent.

Examples 1-6

Compressor oil lubricants meeting the German DIN 51 506 VDL standard were formulated according to amounts in Table 2. The Example formulae were subject to friction losses tests according to modified GFC T014 T 85, ECOTRANS method assessment of the ability of lubricants to reduce friction losses in transmissions, dated 1986 (“Méthode ECOTRANS=évaluation de l'aptitude des lubrifiants à réduire les pertes par frottement dans les transmissions (essais sur machine à engrenages FZG). The GFC T014 T 85 test was modified with gears of 40 mm width (as the 30 mm gears were not available).

The principle of the test was to measure the electric power consumption of a FZG machine, under given loads and at a constant oil temperature, with a given test oil. The power consumption measurements were compared with the power consumption of a given reference oil running under similar conditions.

The tests were run with recalculated loads, proportional to the tooth width, to keep contact forces constant (or as constant as possible), with the loads as indicated in Table 1 below. The oil temperature in the transmission gear case was in the range of about 79-81° C. Test duration from start of load stage ranged from 10-30 minutes.

TABLE 1 Ecotrans CTTG Load Torque Calculated torque Applied Load stage 30 mm gears 40 mm gears torque stage [—] [Nm] [Nm] [Nm] [—] 8 239.3 319.07 302.0 9 6 135.5 180.06 183.4 7 4 60.8 81.06 94.1 5 2 13.7 18.2 13.7 2

TABLE 2 ISO-46 viscosity compressor oil ISO-68 viscosity compressor oil Components Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 PAO-1 90.465 — — 70.775 — — PAO-2 2.45 — — 22.14 — — SN-1 — — 62 — — 30 SN-2 — — 30.915 — — 62.915 FTBO M — 84 — — 28.415 — FTBO H — 11.085 — — 65 — Additive 1 5 5 5 5 5 5 Additive 2 0.5 0.5 0.5 0.5 0.5 0.5 Additive 3 1 1 1 1 1 1 Additive 4 0.5 0.5 0.5 0.5 0.5 0.5 Additive 5 0.05 0.05 0.05 0.05 0.05 0.05 Additive 6 0.02 0.02 0.02 0.02 0.02 0.02 Additive 7 0.01 0.01 0.01 0.01 0.01 0.01 Additive 8 0.005 0.005 0.005 0.005 0.005 0.005 Properties Kin. Viscosity, 45.83 41.42 44.09 67.7 70.6 69.5 40° C., mm²/s Results Ave. from 2 runs, 3 measurements in each Ave., Kw 2.106 1.96 2.188 1.873 1.756 2.162

Test results show that given the same additives, the compressor oil composition comprising isomerized base oils (Examples 2 and 5) demonstrated energy savings ranging from 6.9 to 10.4% (for ISO 46 viscosity) and 6.2 to 18.8% compared to compressor oil compositions of the prior art, including compressor oil compositions containing synthetic oils.

Examples 7-10

Formulae suitable for use as compressor oil with ISO viscosity grade 46 were prepared according to Table 3. The compositions underwent friction losses tests according to modified GFC T014 T 85. The compressor oil composition (Example 7) comprising isomerized base oils demonstrated energy savings ranging from 6.3 to 15.7% compared to prior art compressor oils.

TABLE 3 Components Example 7 Example 8 Example 9 PAO-1 96.37 — — PAO-2 3 — — SN-1 — — 62 SN-2 — — 37.37 FTBO M — 84.37 — FTBO H — 15 — Additive 9 0.55 0.55 0.55 Additive 10 0.07 0.07 0.07 Additive 11 0.01 0.01 0.01 Results Kin. Viscosity, 49.59 44.04 47.78 40° C., mm²/s Results Ave. from 2 runs, 3 measurements in each AVERAGE, kW 1.89 1.77 2.1

Examples 10-16

Formulae suitable for use as compressor oil with ISO viscosity grade 46 were prepared according to Table 4 and a number of tests were conducted including but not limited to MIP-48 Oxidation test, Panel Coker test, Four Ball Wear Test and Rust Test. MIP-48 is a slight modification of the standard IP-48 test. In the original IP-48 test, the testing is done for 2 periods of 6 hrs each with 15-30 hrs of standing time before and between the tests. In the MIP-48 test, the test is run continuously for a period of 24 hrs continuously and then the oil properties are measured. The results are shown in Table 4.

As shown, formulations comprising isomerized base oils demonstrate excellent oxidation stability with comparable viscosity increase but much lower volatility/evaporation loss (Examples 12 and 14) compared to formulations of the prior art, e.g., less than half then evaporation loss of the prior art formulations. Compositions comprising isomerized oils give comparable performance in four ball wear test.

For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or proportions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained and/or the precision of an instrument for measuring the value. Furthermore, all ranges disclosed herein are inclusive of the endpoints and are independently combinable. In general, unless otherwise indicated, singular elements may be in the plural and vice versa with no loss of generality. As used herein, the term “include” and its grammatical variants are intended to be non-limiting, such that recitation of items in a list is not to the exclusion of other like items that can be substituted or added to the listed items.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. All citations referred herein are expressly incorporated herein by reference.

TABLE 4 Example Example Example Example Example Example Example Components (wt. %) Test method 10 11 12 13 14 15 16 Group III 83.39 84.86 — — — — — Group IV 15.10 14.01 — — — 19.78 11.31 FTBO-249 — — 63.95 — — — — FTBO-417 — — 34.92 — — — — FTBO-780 — — — 40.28 27.93 — — FTBO-782 — — — 58.65 66.1 — — PAO-2 — — — — — 74.09 — PAO-3 — — — — — — 82.56 Synthetic Oil 1 — — — — 5.0 — 5.0 Synthetic Oil 2 — — — — — 5.0 — Group II — — — 0.07 0.07 — — Addtive 12 — 0.4 0.4 0.4 0.4 0.4 0.4 Addtive 13 — 0.25 0.25 0.25 0.25 0.25 0.25 Addtive 14 0.25 0.25 0.25 — — 0.25 0.25 Addtive 15 — — — 0.125* 0.125* — — Addtive 16 0.08 0.03 0.03 0.03 0.03 0.03 0.03 Addtive 17 0.05 0.05 0.05 0.05 0.05 0.05 Addtive 18 0.05 0.05 0.05 0.05 0.05 0.05 Addtive 19 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Addtive 20 0.01 0.011 0.011 0.011 — — — API Gravity D287 (R 2006) 35.9 Viscosity, Kinematic D445-06 cSt at 40° C. 64.6 64.6 64.33 63.95 63.59 64.74− 65.44 cSt at 100° C. 10.4 — 10.63 10.64 10.67 — 10.27 Viscosity, Saybolt D445-06 SUS at 100° F. 330 — — — — — — SUS at 210° F. 61.7 — — — — — — Viscosity Index D2270-04 150 143 155 157 158 — 144 Flash Point, D92-05a 254(489) 238 288 302 — — ° C. (° F.) Pour Point, D97-06 −42(−44) −38 −21 −21 — <−52 ° C. (° F.) Color, ASTM D1500-04a L0.5 LT 2 Performance Properties Rust Test, 24 hr, DW D665-06 Pass Pass Pass Pass Pass — Pass Rust Test, 24 hr, D665-06 Pass — Fail Fail Fail — Pass syn water Copper Corrosion D130 (E-2005) 3 h at 121 C. 1B 1B — 1b 1b — — Water Separability D1401-02 40/37/3 40/40/0 41/39/0 40/38/2 — — Minutes to 0 ml — 15 — — 10 15 — — emulsion Foam Tendency/Stability, D892 (E-2007) mL/mL Sequence I (FT/FS) 10/0 10/0 — 10/0 0/0 — — Sequence II (FT/FS) — — — 0/0 30/0 — — Sequence III (FT/FS) — — — 0/0 0/0 — — Air Release, min D3427-06 4 4 2 — — — — Oxidation Stability Hours to 2.0 mg 18,000+ 1 — — — — — KOH/g acid Minutes to 25 psi D2272-02 1800 3038 2990 3597 3307 — — pressure drop IP-48 Oxidation Test, MIP 48 24 hr % Viscosity Increase MIP 48 1.43 2.14 2.02 9.12 9.06 2.27 1.54 % Evaporation Loss MIP 48 1.25 1.0 0.5 1.2 0.7 1.5 0.7 Acid Number Increase MIP 48 −0.29 0.03 0.09 0.1 0.06 −0.01 −0.04 Final Color MIP 48 6 dark brown dark brown Pneurop Oxidation Test DIN 51352 % Evaporation Loss DIN 51353 14.7 11.71 12.42 12.27 9.76 13.07 12.1 Inc. in Conradson Carbon DIN 51354 2.55 2.76 3.08 — — 2.21 2.58 MCRT, ILT 10315, % 3.42 2.34 — — Panel Coker LPTL (see op. conditions) Deposit Weight, mg LPTL 0.6 1.4 0 13.8 0.2 — 0 golden golden Gray/ brown w/ brown w/ gold Beige yellowish purplish film, Panel Picture (color) via Camera Clean 1 Clean 1 green stripping stripping Best 1 Noack Volatility, CEC L-40-T-87 3.29 3.97 — 1.09 1.12 — — % wt loss FZG Fail Stage DIN 51354 9 — — — — — — Four Ball Wear Scar diameter, D4172 0.41 0.53 0.498 0.48 0.456 — — mm, 1800 rpm

TABLE 5 Properties FTBO-M FTBO-H FTBO-249 FTBO-417 FTBO-780 FTBO-782 Kinematic Viscosity @ 40° C., mm²/s 37.92 99.38 32.23 91.64 42.19 86.72 Kinematic Viscosity @ 100° C., mm²/s 7.129 14.84 6.362 13.99 7.901 13.14 Viscosity Index 153 156 153 157 161 152 Cold Crank Viscosity @ −35° C., mPa · s 6,966 — — — 13,547 — Cold Crank Viscosity @ −30° C., mPa · s 3,771 — — — 5,802 — Cold Crank Viscosity @ −25° C., mPa · s 2,200 13,152 — — 2,896 — Pour Point, ° C. −20 −12 −23 −8 −14 −4 n-d-m (ASTM D3238-95 Reapproved 2005) with normalization to 100% total wt % carbon) Molecular Weight, gm/mol (VPO) 540 697 518 737 575 724 Density, gm/ml 0.8222 0.8317 — 0.8009 0.8261 0.8326 Refractive Index 1.459 1.4636 — 1.4461 1.4608 1.4642 Paraffinic Carbon, % 95.47 93.44 — — 93.94 93.86 Naphthenic Carbon, % 4.53 6.56 — — 6.06 6.14 Aromatic Carbon, % 0.00 0.00 — — 0.00 0.00 Oxidator BN, hrs 42.07 35.27 21.29 18.89 37.72 33.52 Sulfur, ppm <2 <1 — — — — Nitrogen, ppm <0.1 <0.1 — — — — Noack Volatility wt. % 2.49 1 2.8 0.7 1.82 0.82 COC Flash Point, ° C. 258 294 — — — — Aniline Point, ° F. — — 263.3 288.9 — — SIMDIST TBP (WT %), F (ASTM D-6352-04) TBP @0.5 805 879 828 947 838 906 TBP @5 836 935 847 963 877 953 TBP @10 850 963 856 972 890 974 TBP @20 869 997 869 990 907 995 TBP @30 884 1021 881 1006 920 1007 TBP @40 897 1042 893 1025 930 1020 TBP @50 913 1060 905 1045 939 1036 TBP @60 930 1079 918 1066 948 1048 TBP @70 947 1099 931 1090 959 1061 TBP @80 973 1122 946 1122 973 1078 TBP @90 1004 1153 962 1168 987 1106 TBP @95 1033 1175 972 1203 998 1140 TBP @99.5 1078 1219 988 1273 1029 1228 FIMS Alkanes 73.1 69.7 68 58.5 55.3 42.7 1-Unsaturation 26.5 29.6 31.2 40.2 34.6 39.4 2-Unsaturation 0.2 0.7 0.7 0.8 8.1 10.3 3-Unsaturation 0 0 0 0 1.9 5.2 4-Unsaturation 0 0 0 0 0.0 1.9 5-Unsaturation 0 0 0 0 0.0 0.4 6-Unsaturation 0.2 0 0 0 0.0 0.0 NMR Analysis: Branching Index 24.29 21.66 23.80 — 23.09 20.12 Branching Proximity 17.94 21.45 18.87 — 23.40 28.02 Alkyl Branches per Molecule 3.33 3.7 3.75 — 3.36 3.89 Methyl Branches per Molecule 2.62 2.85 — 3.43 2.77 3.26 FCI 6.92 10.68 — 12.59 9.61 14.49 Alkyl Branches per 100 Carbons 8.63 7.43 10.13 8.38 8.17 7.53 Methyl Branches per 100 Carbons 6.79 5.73 6.55 6.74 6.30 Wt % Olefins by Proton NMR 1.38 2 3.49 — 0.00 0.00 Wt % Aromatics <0.001 <0.001 — — — — Total Wt % Molecules with Cycloparaffinic 26.9 28.3 — — — — Functionality Monocycloparaffins/Multicycloparaffins 62.8 39.4 44.6 48.8 3.5 2.2 

1. A compressor lubricant composition, comprising: (i) 80 to 99.999 weight percent of an isomerized base oil; and (ii) 0.001-20 weight percent of at least an additive selected from an additive package, oxidation inhibitors, pour point depressants, metal deactivators, metal passivators, anti-foaming agents, friction modifiers, anti-wear agents, and mixtures thereof; wherein the isomerized base oil has consecutive numbers of carbon atoms, less than 0.05 wt. % aromatics, a ratio of molecules with monocycloparaffinic functionality to molecules with multicyloparaffinic functionality greater than 2, and wherein the weight percents of (i) and (ii) are relative to the total weight of the composition.
 2. The compressor lubricant composition of claim 1, wherein a compressor that employs the composition consumes at least 2% less power than a compressor employing a lubricant composition without the isomerized base oil.
 3. The compressor lubricant composition of claim 1, wherein a compressor that employs the composition consumes at least 5% less power than a compressor employing a lubricant composition without the isomerized base oil.
 4. The compressor lubricant composition of claim 1, wherein a compressor that employs the composition consumes at least 10% less power than a compressor employing a lubricant composition without the isomerized base oil.
 5. The compressor lubricant composition of claim 1, wherein the isomerized base oil has a viscosity index (VI) of at least
 140. 6. The compressor lubricant composition of claim 1, wherein the isomerized base oil has a VI of at least
 160. 7. The compressor lubricant composition of claim 1, wherein the isomerized base oil has a flash point of at least 250° C.
 8. The compressor lubricant composition of claim 1, wherein the composition has a RPVOT as measured according to ASTM D2272-02 of greater than 600 minutes.
 9. The compressor lubricant composition of claim 8, wherein the composition has a RPVOT as measured according to ASTM D2272-02 of greater than 1000 minutes.
 10. The compressor lubricant composition of claim 1, wherein the composition meets at least one of German standard DIN 51 506 class VDL, ISO/DP 6521-L-DAB and ISO 6743-3A-DAC.
 11. The compressor lubricant composition of claim 1, wherein the composition has an evaporation loss of less than 1% per MIP-48 Oxidation Test (24 hrs.).
 12. The compressor lubricant composition of claim 1, wherein the composition has an evaporation loss of less than 0.75% per MIP-48 Oxidation Test (24 hrs.).
 13. The compressor lubricant composition of claim 1, wherein the composition has a RPVOT of greater than 300 minutes according to ASTM D2272-02.
 14. The compressor lubricant composition of claim 1, wherein the composition has a RPVOT of greater than 600 minutes according to ASTM D2272-02.
 15. The compressor lubricant composition of claim 1, wherein the composition separates from water in less than 60 minutes as measured according to ASTM D-1401-2002.
 16. The compressor lubricant composition of claim 1, further comprising 5 to 20 weight percent based on the total weight of the composition, at least a lubricant base oil selected from vegetable oils and Group I, II, III, IV, and V lubricant base oils as defined in the API Interchange Guidelines, and mixtures thereof.
 17. The compressor lubricant composition of claim 1, wherein the isomerized base oil has an auto-ignition temperature of at least 360° C.
 18. The compressor lubricant composition of claim 1, wherein the isomerized base oil is a Fischer-Tropsch base oil.
 19. The compressor lubricant composition of claim 1, wherein the composition comprises at least isomerized base oil having a kinematic viscosity at 100° C. between 6.5 and 16 mm²/s and a kinematic viscosity at 40° C. between 25 mm²/s and 120 mm²/s.
 20. The compressor lubricant composition of claim 1, wherein the isomerized base oil has an Oxidator BN of 15 to 50 hours; and a Noack volatility in wt. % of 0.5 to 5 as measured by ASTM D5800-05 Procedure B.
 21. The compressor lubricant composition of claim 1, wherein the isomerized base oil has a pour point in the range of −10 and −30° C.
 22. The compressor lubricant composition of claim 1, wherein the isomerized base oil is a Fischer-Tropsch base oil having less than 0.05 wt. % aromatics and a molecular weight of 500 to 800 by ASTM D 2503-92 (Reapproved 2002).
 23. A method for operating a compressor, the method comprising using a compressor lubricant composition comprising: (i) 80 to 99.999 weight percent of an isomerized base oil; and (ii) 0.001-20 weight percent of at least an additive selected from an additive package, oxidation inhibitors, pour point depressants, metal deactivators, metal passivators, anti-foaming agents, friction modifiers, anti-wear agents, and mixtures thereof; wherein the isomerized base oil has consecutive numbers of carbon atoms, less than 0.05 wt. % aromatics, a ratio of molecules with monocycloparaffinic functionality to molecules with multicyloparaffinic functionality greater than 2, and wherein the weight percents of (i) and (ii) are relative to the total weight of the composition; wherein the compressor lubricant composition consumes at least 2% less power than the compressor employing a lubricant composition without the isomerized base oil.
 24. The method of claim 23, wherein the compressor using the composition comprising: (i) 80 to 99.999 weight percent of an isomerized base oil consumes at least 5% less power than the compressor employing a lubricant composition without the isomerized base oil.
 25. The method of claim 23, wherein the compressor using the composition comprising: (i) 80 to 99.999 weight percent of an isomerized base oil consumes at least 10% less power than the compressor employing a lubricant composition without the isomerized base oil. 